Convert pixel value to HU

How can I change a voxel value of a Micro CT image series to HU units ?

i need to change the voxel value and the header in dicom to use the new dicom in the treatment planning system

the linear equation i will be used to change the voxel is

y = 0.7966x-568.5

[Ahmad Abbas]

% this is the code i used to create histogram, which help me to create the equation (tmp11) which then i convert the pixel value to HU ( i am not sure if it is correct or not ) 
% i am trying to save the result with the metadata and changes, please can someone help
clear
myFolder = 'C:\Users\Admin\Desktop\MATLAB\Crop cochlea';
filePattern = fullfile(myFolder, '*dcm');
theFiles = dir(filePattern);
crop=zeros(209,218,394);
for k = 1 : length(theFiles)
    baseFileName = theFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf(1, 'Now reading %s\n',fullFileName);
    x = dicomread(fullFileName);
    crop(:,:,k)=x;
end
%histogram(crop)
tmp11 = min(max (0.7966*crop -568.5, -1000),4096); 
hu = uint16(tmp11);

Answer 1

[Gouri Chennuru]

Hi Ahmad,

In order to convert the data found in CT data to Housefield Units you have to apply a linear transformation to the data.

The equation, which is used for converting into HouseField Units,

HU = pixel_value*slope +intercept

The tags are alse called as Rescale Slope and Rescale Intercept.

The slope and intercept are found in the DICOM file itself and you can read the DICOM image to MATLAB using “dicomread”.

Thanks & Regards,

Gouri Chennuru.

[Walter Roberson]

And see

https://www.mathworks.com/matlabcentral/answers/153570-how-can-i-obtain-hounsfield-units-hu-from-a-dcm-image

Technical reference links given at https://www.mathworks.com/matlabcentral/answers/114123-how-to-calculation-hounsfield-unit#answer_127872